Serrated tearing edges



169 1965 Y J- s. REILLY 3,169,65

SERRATEID TEARING EDGES Filed Nov. 14, 1962 [nvenfior /6 John 3. Reilly By his/Htorney [z 10 5 20 F. w

United States Patent 3,169,685 SERRATED TEG EDGES John S. Reilly, Beverly, Mass, assignor to United Shoe This invention relates to improved serrated edge portions for tearing sheet material and particularly to such edges constituting a sheet severing portion of a dispensing carton for a roll of sheet material.

Dispensing cartons for rolled sheet material such as wax paper or aluminum foil are commonly provided with a cutting edge affixed to a wall of the carton for severing desired lengths of the sheet material. In the past these cutting edges have been strips of metal serrated along the exposed edge and stapled or otherwise fixed to the carton wall. Metal strips have sharp corners or edges which may inflict cuts and scratches in handling the carton. Also such metal strips are relatively expensive.

It has been proposed to eliminate these difficulties by impregnating an edge portion of a fibrous carton blank with a hardening agent and to serrate the edge. This hardened and serrated edge then constitutes a tearing edge portion integral with the carton. However, it has not been practical under usable manufacturing procedures to impregnate the hardening agent through the thickness of the carton material or to associate such material in a manner to secure effective cooperation of the hardening agent and carton material. Previous cutting edges have tended to lose their ability to tear cleanly after very little use because of blunting or distortion of the serrations by the sheet material.

It is an object of the present invention to provide a container having an improved serrated edge portion for tearing sheet material where the teeth constituting the serration retain a superior tearing ability on extended use.

To these ends and in accordance with the present invention a hard tearing edge and cooperative integral stiffening reinforcement is formed on marginal face and serrated edge surface portions of a fibrous sheet. Hard resinous material is deposited to form the novel edge and reinforcement by pressing marginal face portions of a fibrous sheet adjacent a serrated edge into a thin molten layer of resinous material on a hot carrier surface. The sheet displaces portions of the molten layer and causes it to deposit on desired portions of the face and edge of the sheet. After removal of the sheet from the molten layer the material deposited hardens to form a superior reinforced tearing edge firmly associated with the sheet.

The invention will be described further in conjunction with the accompanying drawings forming part of the disclosure in which:

FIG. 1 is a plan view of a section of sheet material showing resin deposited on the face and serrated edge portions of a sheet to provide a reinforced tearing edge;

FIG. 2 is a cross section taken on the line II-Ii of FIG. 1 and on an enlarged scale showing the relation of the deposited resin on the face and serrated edge surface portions of a sheet material;

FIG. 3 is a diagrammatic elevational view illustrating an arrangement of apparatus through which serrated edge sheet material may be passed to form the reinforced edges;

FIG. 4 is a partial elevational view at right angles to the direction of FIG. 3 and on a larger scale, showing the relation of certain parts of the apparatus of FIG. 3 with serrated edge sheet material being brought into association with molten resinous material;

arsassis Patented Feb. 16, 1965 FIG. 5 is a fractional view on an enlarged scale show ing the application of molten resinous material to a serrated edge sheet in accordance with one form of the present invention;

FIG. 6 is a fractional view on an enlarged scale showing the application of molten resinous material to a serrated edge sheet in accordance with another form of the present invention; and

FIG. 7 is an enlarged view of a serrated edge sheet and reinforcing resinous material on its face and edge surface portions as formed according to the procedure shown in FIG. 6.

In the present tearing edge, relatively thick deposits 10 of hard resinous material on the edge portions 12 of the teeth 14 constituting serrations of a fibrous sheet 16, e.g. a cardboard carton blank, provide points which aid in tearing sheet material. The teeth 14 should be at least about inch in height and have a pitch of at least 4 inch. A film 18 of hard resinous material integral with the deposits 10 and extending along marginal portions of the surface of one face 20 of the sheet 16 from the points of the teeth 14 to a line at least about 4 inch below the bottom of the teeth serves to unify the deposits 10 into an effective tearing edge. The film 18 may be as little as 0.002 inch in thickness. The deposits 10 on the edge portions of the teeth 14 and the film 18 conform to and are in intimate adhering engagement with the fibrous sheet 16 so that the film 18 and edge deposits 10 form with the fibrous sheet 16 beam structures for the teeth 14 which are strongly resistant to bending. The fibrous sheet 16 may be any of the usual carton materials such as cardboard, chipboard, sulfite board and the like and will ordinarily be from about 0.015 to about 0.02 inch or more in thickness. The thickness of the deposit 10 on the edge portions 12 of the teeth adjacent the points may be from about 0.005 to about 0.020 or more and may taper to a less thickness towards the base of the teeth. The thickness adjacent the points coupled with the firm support obtained through the cooperation with the deposits 10 of the film 18 and the fibrous material resist crushing or deformation under the stresses developed in tearing of sheet material which have blunted or deformed previous stiffened serrations of fibrous cartons.

Resinous materials for deposit on marginal face portions and teeth edge portions of a fibrous sheet 16 are those readily fusible to a molten fluid having a viscosity suitable for application in the desired relation and solidifying rapidly on cooling to a strong tough condition. Resins having a viscosity in molten condition of preferably at least about 20,000 cps. as determined at 225 C. with a Brookfield viscometer using a No. 4 spindle and speed of rpm. have been useful using a smooth surfaced applicator and conventional fibrous material carton blanks; but somewhat lower or higher viscosity materials may be used. Excellent tearing edges have been ob tained with resinous material having in cooled and hardened condition a hardness in excess of '25 on the Shore D scale and a tensile strength preferably of about 3,000 lbs. per square inch and higher.

Resins having these characteristics include relatively high molecular weight polyesters from reaction of one or more dicarboxylic acids such as terephthalic acid and isophthalic acid with lower alkylene glycols such as ethylene glycol or butylene glycol, polyesteramides, for example, adipic polyesterarnides in which the hydroxy component is 1,6 hexane diol, 1,4 butane diol or ethylene glycol, and polyamide resins such as the nylon materials and polyamides from condensation of dimerized oleic acid and ethylene diamine or polyalkylene polyamines. Preferred resinous polyesters include condensates of a lower alkylene glycol for example, 1,4 butane diol with mixed terephthalic and isophthalic acid components with the acid components in the molar ratio of from about 1: I

to about 4:1. These preferred polyesters will be condensed to provide melting points of from about 80 to about 200C. 7 i i t Deposition of relatively thick deposits 10 of resinousmaterial along the edges of the teeth and a relatively thin film 18 along the face 20 of the fibrous sheet may be: effected by pressing'marginal portions along the serrated edge of-a face 20 of the sheet 16 into a layer 22 of molten adhesive on a hot surface 24. In general, the molten layer 22 may be from about A; to about /2 the thickness of the fibrous sheet, preferably from 0.002" to 0.010 in thickness The exact thickness to be used depends upon the thickness of. the sheet material 16 .on which the material'is to be deposited and on the amount of resin. which it is desired to deposit. Depositing the material from such a supported layer 22 of resin rather than from a molten body of substantial thickness or from a nozzle is important since the action involved is, at least in part, squeezing of the molten material from between the surface 20 of the fibrous sheet 16 and the carrier surface 24 on which the layer 22 of molten resin is supplied. The

' squeezed-out material rises above the level of the adhesive layer 22 so that it can wet and form relatively thick deposits '10 on the edge portions 12 of the teeth 14. Also this enables control of the thickness of the unifying and reinforcing film 13 on the face portions of the sheet material while at the same time providing substantial deposits 10 of material on the tooth edge portions 12.

Although other apparatus may be used, a hot melt applicator similar to that shown in the patent to'Paulsen 2,726,629 of December 13, .1955, has been found useful. In this device solid thermoplastic resin material in the form of a rod 32 is fed through a channel 34 into a heated chamber 36 in which is mounted a disk or wheel of whichthe circumferential surface .24 serves as a carrier surface for the resin layer 22 and defines, with the walls of the chamber 36, a passageway 42 in which the thermoplastic material is melted and spread on the surface 24 of the wheel 38. As shown in FIGS. 3 and 4, the marginal portions of the face 20 of the fibrous sheet 16 are pressed into contact with the layer 22 of adhesive on the wheel 38 by a guide wheel 46 disposed to press against the fibrous sheet 16 along a line spaced slightly inward of the bottoms of the teeth 14. a

It is preferred that the direction of feed of the fibrous sheet '16 be counter to the direction of movement of the surface 24 of the disk or wheel 33 at the point of contact as shown in FIG. 5 in order that the applicator wheel 38 may wipe on a smooth'film 18 of molten material in wetting engagement on the surface 20 of the sheet material.

In this procedure the edge portions 12 of the teeth 14 on' the side of the teeth in which the sheet material is moving plow up molten material from the layer 22 on the surface 24 of the diskor wheel, and the plowed-up material is deposited primarily on these edge portions. 1t

'wil-l'be noted that the edge portions 12 adjacent the points of the teeth 14 collect the molten material deposited by the sarne linear distance of movement of'the wheel as do the edge portions 12 adjacent the bottoms of the teeth.

Since the moltenmaterial on the surface 24 of the wheel wheel.

Although it is preferred to use a direction of feed of the sheet material 16 counter to that of the movement of the surface 40 carrying the molten layer 44, it is possible to operate as shown in FIG. 6 with the carrier surface 24 moving in the same direction'as the sheet material 16. With this mode of operation, deposition of'molten material occurs due to the displacement of molten material of the-layer when face portions20 of the sheet material 16 are pressed towards the carrier surface. Thisdisplaced material flows up above the'general level of molten material on the surface and deposits on both edges 12 of the teeth 14 as shown in 'FIGS. 6 and 7. It is to be noted that in this operation it has beenfound generally preferable to use a somewhat thicker layer ofvmolten material on the carriersurface such as the surface of an applicator Also, although the same greaterdeposition adjacent the points of the teeth is not secured in this procedure as was obtained in the procedure noted above, using counter movement, nevertheless, since the material deposits on both edges of the teeth it has been found to provide adequate'tooth reinforcement. .Howevcr, the op 'eration is less desirable from certain points of view such as its normal requirement of a higher quantity of material to achieve the same reinforcement as obtained with a counter movement and some difficulties in maintaining uniformity of deposition.

By way of illustration and not by way of limitation, there has been used a resinous polyester formed by condensation and polymerization of 4 mols of terephthalic acid and 1 mol of iso-phthalic acidwith' 1,4 butane diol and having a melting point of 190 C., a Shore D hardness of about 75, a tensile strength of 3000 pounds per square inch and a viscosity at 225 C. of 70,000 cps. (Brookfield viscometer using lspindle at 120 r.p.m.). This material was deposited on the serrated marginal edge portions of a carton blank of 0.015 inch thick cardboard with A inch 'highteeth by an applicator wheel'having a circumference of one foot rotating 'in a reverse direction to that of the movement of the sheet material. An 0.006" thickness of molten resin material at a temperature of 430 F. on theapplicator surface was effective to deposit a film of from .006 to .007" thickness came face of the sheet material using a 500 f0ot per minute rate of feed for the sheet material and a reverse circumferential'speed of 500 feet per minute of the applicator wheel. in this operation the resin deposits. on the edges of the teeth I ranged up to about .010" in thickness.

formation of fine threads of material extending between adjacent the points is not consumed by deposition on sig nificant'areas ofithe face 20 of the sheet material 16, thereis available and is collected by the edge portions near the points a greater quantity of molten material than is collected near the bottoms of the teeth. This greater quantity of material provides a thicker and stronger cross section adjacent the points where it is needed to'initiate tearing then is deposited adjacent the bottoms of the teeth. Also since, as shownin FIG. 5, the material is deposited primarily on only one edgeof each tooth a strong thick edge isobtained with less material; After deposition of toe molten material on the blank, the molten material quickly cools and hardens to form the desired reinforced tooth l structure.

the points of adjoining teeth.

Having thus described my invention, what I claim as new anddesire to secure by Letters Patent of the United States is: V

1. In a tearing edge including fibrous sheet having a serrated edge portion of a deposit 'of hardened thermoplastic material extending along a face of the cardboard adjacent the serrations and portions of hardened thermoplastic material integral with said deposit covering edge surfaces 'of the serrations, said portions of thermoplastic material covering said edge surfaces being supported in firm relation on said fibrous sheet by said deposit of hardened material against the stresses encountered of tearing sheet material.

V 2. In a tearing edge including a fibrous sheet having a serratededge portion, a deposit of hardened thermoplastic material extending in a band along a faceof thecardboard adjacent the serrated edge and extending below the base of the serrations and portions of hardened thermoplastic material integral With said deposit on edge surfaces of the serrations, said portions of thermoplastic material on said edge surfaces being supported in firm relation on said fibrous sheet by said deposit of hardened material against the stresses of tearing sheet material.

3. In a tearing edge including cardboard sheet having serrations at least inch in height along an edge, a relatively thin deposit of hardened thermoplastic material extending in a band along a face of the cardboard adjacent the serrated edge and extending below the base of the serrations and relatively thicker portions of hardened thermoplastic material integral with said first-mentioned deposit on edge surfaces of the serrations, said thicker portions being supported in firm relation on the cardboard sheet by said thinner layer against the stresses of tearing sheet material.

4. In a tearing edge including a cardboard sheet having serrations at least & inch in height along an edge, a relatively thin deposit of hardened thermoplastic material extending in a band along a face of the cardboard adjacent the serrated edge and extending below the base of the serrations and relatively thicker portions of hardened thermoplastic material integral with said first-mentioned deposit on edge surfaces of the serrations, said thermoplastic material having a Shore D hardness of at least 25 and a tensile strength of at least about 3000 pounds per square inch, said thicker portions being supported in firm relation on the cardboard sheet by said thinner layer against the stresses of tearing sheet material.

5. In a tearing edge including a cardboard sheet having serrations at least inch in height along an edge, a relatively thin deposit of hardened thermoplastic material extending in a band along a face of the cardboard adjacent the serrated edge and extending at least $5 inch below the base of the serrations and relatively thicker portions of hardened thermoplastic material integral with said first-mentioned deposit primarily on one of the tWo edge surfaces of the individual serrations, said thermoplastic material having a Shore D hardness of at least 25 and a tensile strength of at least about 3000 pounds per square inch, said thicker portions being supported in firm relation on the cardboard sheet by said thinner layer against the stresses of tearing sheet material.

6. In a tearing edge including cardboard sheet having serrations at least inch in height along an edge, a relatively thin deposit of hardened thermoplastic material extending in a band along a face of the cardboard adjacent the serrated edge and extending at least inch below the base of the serrations and relatively thicker portions of hardened thermoplastic material integral with said first-mentioned deposit on both edge surfaces of the serrations, said thermoplastic material having a Shore D hardness of at least 25 and a tensile strength of at least about 3000 pounds per square inch, said thicker portions being supported in firm relation on the cardboard sheet by said thinner layer against the stresses of tearing sheet material.

References Cited in the file of this patent UNITED STATES PATENTS 1,712,604 Cosgrove May 14, 1929 1,752,454 Overbury Apr. 1, 1930 1,887,912 Begle Nov. 15, 1932 1,915,736 Hurlbut June 27, 1933 1,952,431 Gluck et a1. Mar. 27, 1934 2,000,867 Spaldo May 7, 1935 2,633,985 Meyer Apr. 7, 1953 3,079,054 Heinz Feb. 26, 1963 

1. IN A TEARING EDGE INCLUDING FIBROUS SHEET HAVING A SERRATED EDGE PORTION OF A DEPOSIT OF HARDENED THERMOPLASTIC MATERIAL EXTENDING ALONG A FACE OF THE CARDBOARD ADJACENT THE SERRATIONS AND PORTIONS OF HARDENED THERMOPLASTIC MATERIAL INTEGRAL WITH SAID DEPOSIT COVERING EDGE SURFACES OF THE SERRATIONS, SAID PORTIONS OF THERMOPLASTIC MATERIAL COVERING SAID EDGE SURFACES BEING SUPPORTED IN FIRM RELATION ON SAID FIBROUS SHEET BY SAID DEPOSIT OF HARDENED MATERIAL AGAINST THE STRESS ENCOUNTERED OF TEARING SHEET MATERIAL. 